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From: pmk@prometheus.UUCP (Paul M Koloc)
Newsgroups: net.physics
Subject: Re: lightning bursts
Message-ID: <156@prometheus.UUCP>
Date: Thu, 1-Aug-85 02:51:29 EDT
Article-I.D.: promethe.156
Posted: Thu Aug 1 02:51:29 1985
Date-Received: Fri, 2-Aug-85 08:22:39 EDT
References: <3305@decwrl.UUCP>
Organization: Prometheus II Ltd., College Park, MD
Lines: 57
> Once one lightining strike has ionized the air it leaves a path of lesser
> resistance than existed before. That alone should make successive strikes
> more probable until the available potential has diminished. Then air
> turbulence eliminates the ionized path and the max potential must rebuild.
>
> This does not explain why paths OTHER than the first one appear to be part
> of the cluster of strikes that follow the first one, a phenomena I have
> observed myself (from the ground). My suggestion is that there is
> leakage current moving through the air that preceeds the strike and that
> they are ALL about ready to produce stike paths. Which one goes first is
> therefore random and the burst is NOT "caused by" the first one.
>
> Rick Merrill 617-493-3751
Cloud to ground lightning generates a vaccuum channel which persists for
a couple of milliseconds. "M" strokes can light up the vacuum channel
sort of like a florescent tube without the phosphor. Consequently such
strokes are only seen using image intensifier fast optics. It is
more likely that multiple strokes which can be seen by rapidly moving
ones eye back and forth so as to spacially separate the strokes on
the retina, probably track along the same breakdown path (stationary
with respect to the air mass), because of the copius generation of
ozone and nitrous oxides which are which are quit unstable. Also, oxygen
and these compounds are electrophilic and will attach electrons to
form negative ions. These ions give up free electrons in a relatively
weak field as far as lightning potentials go.
The triggering of ancillary cloud to cloud lightning probably occurs
because once a cloud to ground stroke occurs the charge of the
adjacent clouds redistributes and this produces a series of cloud to
cloud lightning. The potential to generate a discharge is less in
clouds with heavy rain so that such charge redistribution can also
signal the potential build up it takes to generate a new cloud to ground
stroke. So that cloud to cloud strokes can preceed a cloud to ground
stroke.
Dry air strokes often generate the biggest wallop. They usually come
from the leading edge of thunderheads along a fast squall line.
A boys camera (wide angle lens looks straight up) took a picture
out west (krider at arizona) that showed a stroke which had feed branches
spreading out radially for forty miles. And there are "bright" lightning
strokes off the coast of Japan that have triggered nuclear bomb monitors
in satellites. Suggested energies were well over 10^11 joules.
One more interesting thing. Charge on tiny rain drops tends to prevent
their merging. So usually two minutes after a nearby heavy stroke
(rain drop fall time), the rain will start or increase significantly.
That's more reliable at the beginning five or ten minutes of a rain storm.
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